This project will combine recent advances in electrochemical biosensor technology achieved in many laboratories with unique silicon microprobe technology developed in our laboratory, to produce low cost disposable biosensor microprobes for painless continuous measurement of blood glucose concentration. Impressive glucose biosensor R&D progress has not yet resulted in commercial devices for painless in vivo applications because other workers in "needle biosensors" have used conventional configurations and fabrication methods. The high cost and size (hypodermic needle diameters, requiring painful surgical implantation) of conventional biosensors requires that they last a long time. The principal approach taken by others to make them practical is to extend their lifetimes toward six months of operation, but this effort has produced only slow incremental progress. The strength of the proposed approach lies in the combination of biosensors and silicon microprobes. By rendering insertion and removal completely painless (which has been shown in clinical trials) and sharply reducing the cost, disposable integrated biosensor microprobes employing electrochemical sensor technology at its present state of development become commercially practical. Integration of biosensors with silicon microprobes comparable in cross-section to a human hair to provide a practical technique for painless blood testing is not restricted to glucose but is an enabling technology applicable to many other analytes.